Which of following observations would convince many Greek astronomers that our Earth does move through space?

Question

Which one of the following observations would convince many Greek astronomers that our Earth does move through space?

a. Retrograde motion of Mars
b. Stellar parallax
c. Phases of Venus
d. Sunspots on the Sun
e. Ice caps on Mars

Answer 1

b. Stellar parallax

The idea that Earth moves around the Sun, instead of the other way around, was held by some ancient Greek astronomers (Aristarchus, I believe, but I could be wrong). But the biggest argument against it was that they couldn't detect any parallax of nearby stars. Of course, they didn't realize just how far away those stars really are!

a. is wrong - they knew about Mars' retrograde motion.

c. to my knowledge was never anything considered by the ancient Greeks. Besides, it only proves that Venus orbits the Sun, not that we do - they could have easily modified their geocentric model to have other planets orbiting the Sun, while the Sun still orbits us (Tycho Brahe, among others, believed this was true, by the way)

d. and e. are quite obviously wrong answers.

B is the best answer, even though arguements could be made for a and c.

Answer 2

I assume you're talking about ancient Greek astronomers.
It isn't A, since they knew about retrograde motion. They even thought that retrograde motion could be caused by things revolving about the sun. But, they also thought that if the earth was moving, they would see stars at different distances move relative to each other. They didn't observe this though. This is because the stars are much farther than they thought was possible and the parallax was undetectable by the naked eye.
For this reason I was tempted to pick B. While it is true that observing Stellar prallax would probably convince them that things go aroudn the sun, they wouldn't have been able to detect the parallax.
The phases of Venus on the other hand proved that venus orbits the sun and not earth. It's a short leap from there to saying other things can orbit the sun also.

I think C is the best answer.

Answer 3

The Greeks observed (a) and still constructed a geocentric system. Check up on "epicycles".

(d) and (e) would not be evidence for the Earth moving, even to modern scientists.

(c) is evidence for Venus moving through space, but if the Greeks had observed it, I bet they could have added enough epicycles to their geocentric model to account for it.

(b) is only evidence for the Earth moving if you accept that some stars are much closer than others. The Greeks thought that all the stars were the same distance away, so if they had observed stellar parallax they would have needed to alter two of their assumptions, not just one, to explain it as we understand it. They might have constructed an explanation for it with stellar epicycles, rather than abandon the geocentric theory.

So although (b) is probably the expected answer, no examiner could safely claim that stellar parallax would have CONVINCED the Greeks that the Earth moved through space.

Answer 4

A. Retrograde motion of Mars
and
B. Stellar parallax

A alone does not prove that the earth moves, as seen in the model of a geocentric universe here:
http://www.lasalle.edu/~smithsc/Astronomy/retrograd.html
However with B, stellar parallax it is possible to prove the movement of the earth.
http://en.wikipedia.org/wiki/Parallax
After taking into consideration B, that the earth moves, A will prove that both the Earth and Mars move.

Answer 5

b. Stellar parallax.
All the others can be explained with a geocentric model, given enough complications, like epicycles.
Inability to measure parallax was the main reason Galileo was unable to make his case. It turns out to be too small to measure with tools available in Galileo's time, much less by the earlier Greeks, because the stars are much farther away than anyone suspected back then.

Answer 6

None of the above...the Greeks already knew about the retrograde motion of Mars. They didn't have instruments capable of making any of the other observations.

Answer 7

B

Parallax, or more accurately motion parallax (Greek: παραλλαγή (parallagé) = alteration) is the change of angular position of two stationary points relative to each other as seen by an observer, due to the motion of an observer. Simply put, it is the apparent shift of an object against a background due to a change in observer position.

Edit: (hey who gave me that thumbs down? anyway...)
I don't think it's 'A' because using a "Ptolemaic Explanation" you can still say the Earth is stationary. More on "Ptolemaic Explanation" see: http://www.lasalle.edu/~smithsc/Astronomy/retrograd.html

Answer 8

i assume you propose historic Greeks. modern Greek astronomers have faith that the earth is shifting!!! properly, a,c,d,e are actually not seen and not making use of a telescope. B become suggested by ability of historic greeks and defined by ability of making use of epicycles. nonetheless if I had to decide for one in all Abcde i might decide for B

Answer 9

Hi. I don't think the ancient Greeks knew about anything but A.

Answer 10

hmm. Probably 'a'

It's not B since stellar parallax is true whether the eart moves or not. Phases of venus is true if Venus moves (the Earth doesn't have to) and the last 2 are just silly